The structural maintenance of chromosomes (SMC) complex Smc5/6 is based on a heterodimer of two SMC subunits, Smc5 and Smc6, and six non-Smc element subunits, Nse1-6, all of which are essential for cell viability in most organisms. Smc5/6 safeguards genome integrity via different mechanisms, including stabilization of stalled replication forks, resolution of recombination intermediates, and maintenance of nucleolar integrity. However, the essential functions of Smc5/6 remain elusive. The aim of the present work was to understand when in the cell cycle the crucial functions of Smc5/6 are manifested and to identify them. Through the use of cell cycle regulated alleles, which enabled the restriction of various Smc5/6 subunits expression to either S or G2/M phases of the cell cycle, we uncovered that the essential roles are executed postreplicatively in G2/M. By further genetic screens, molecular approaches and genome-wide studies, we identified three chromosome topology and recombination-related processes that are crucially sensitive to low amounts of Smc5/6 specifically in G2/M. First, Smc5/6 plays a topological role affecting the formation and/or the resolution of Rad5-Mms2-Ubc13 chromatin structures that are later engaged by Sgs1-Top3-Rmi1. Second, Smc5/6 facilitates an epigenetic pathway that ensures silencing of specific loci, such as repetitive DNA regions, thereby preventing unrestrained recombination. Third, Smc5/6 has an anti-fragility function, facilitating replication through natural pausing elements and site-specific replication fork barriers and preventing their breakage in mitosis during chromosome segregation.
ESSENTIAL POSTREPLICATIVE FUNCTIONS OF THE SMC5/6 COMPLEX / D. Menolfi ; supervisore interno: M. Foiani, D. Branzei ; supervisore esterno: P. Pasero, D. Branzei. UNIVERSITA' DEGLI STUDI DI MILANO, 2015 Mar 18. 26. ciclo, Anno Accademico 2014. [10.13130/d-menolfi_phd2015-03-18].
ESSENTIAL POSTREPLICATIVE FUNCTIONS OF THE SMC5/6 COMPLEX
D. Menolfi
2015
Abstract
The structural maintenance of chromosomes (SMC) complex Smc5/6 is based on a heterodimer of two SMC subunits, Smc5 and Smc6, and six non-Smc element subunits, Nse1-6, all of which are essential for cell viability in most organisms. Smc5/6 safeguards genome integrity via different mechanisms, including stabilization of stalled replication forks, resolution of recombination intermediates, and maintenance of nucleolar integrity. However, the essential functions of Smc5/6 remain elusive. The aim of the present work was to understand when in the cell cycle the crucial functions of Smc5/6 are manifested and to identify them. Through the use of cell cycle regulated alleles, which enabled the restriction of various Smc5/6 subunits expression to either S or G2/M phases of the cell cycle, we uncovered that the essential roles are executed postreplicatively in G2/M. By further genetic screens, molecular approaches and genome-wide studies, we identified three chromosome topology and recombination-related processes that are crucially sensitive to low amounts of Smc5/6 specifically in G2/M. First, Smc5/6 plays a topological role affecting the formation and/or the resolution of Rad5-Mms2-Ubc13 chromatin structures that are later engaged by Sgs1-Top3-Rmi1. Second, Smc5/6 facilitates an epigenetic pathway that ensures silencing of specific loci, such as repetitive DNA regions, thereby preventing unrestrained recombination. Third, Smc5/6 has an anti-fragility function, facilitating replication through natural pausing elements and site-specific replication fork barriers and preventing their breakage in mitosis during chromosome segregation.File | Dimensione | Formato | |
---|---|---|---|
phd_unimi_R09393.pdf
Open Access dal 18/08/2016
Descrizione: Tesi Dottorato
Tipologia:
Tesi di dottorato completa
Dimensione
64.09 MB
Formato
Adobe PDF
|
64.09 MB | Adobe PDF | Visualizza/Apri |
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.